// This may look like C code, but it is really -*- C++ -*-
/* 
Copyright (C) 1988 Free Software Foundation
    written by Dirk Grunwald (grunwald@cs.uiuc.edu)

This file is part of the GNU C++ Library.  This library is free
software; you can redistribute it and/or modify it under the terms of
the GNU Library General Public License as published by the Free
Software Foundation; either version 2 of the License, or (at your
option) any later version.  This library is distributed in the hope
that it will be useful, but WITHOUT ANY WARRANTY; without even the
implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE.  See the GNU Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#ifndef _RNG_h
#define _RNG_h 1
#ifdef __GNUG__
#pragma once
#pragma interface
#endif

#include <assert.h>
#include <math.h>

union PrivateRNGSingleType {		   	// used to access floats as unsigneds
    float s;
    unsigned long u;
};

union PrivateRNGDoubleType {		   	// used to access doubles as unsigneds
    double d;
    unsigned long u[2];
};

//
// Base class for Random Number Generators. See ACG and MLCG for instances.
//
class RNG {
    static PrivateRNGSingleType singleMantissa;	// mantissa bit vector
    static PrivateRNGDoubleType doubleMantissa;	// mantissa bit vector
public:
    RNG();
    //
    // Return a long-words word of random bits
    //
    virtual unsigned long asLong() = 0;
    virtual void reset() = 0;
    //
    // Return random bits converted to either a float or a double
    //
    float asFloat();
    double asDouble();
};

#if defined(__OPTIMIZE__) || defined(USE_LIBGXX_INLINES)


inline float RNG::asFloat()
{
    PrivateRNGSingleType result;
    result.s = 1.0;
    result.u |= (asLong() & singleMantissa.u);
    result.s -= 1.0;
    assert( result.s < 1.0 && result.s >= 0);
    return( result.s );
}
	
inline double RNG::asDouble()
{
    PrivateRNGDoubleType result;
    result.d = 1.0;
    result.u[0] |= (asLong() & doubleMantissa.u[0]);
    result.u[1] |= (asLong() & doubleMantissa.u[1]);
    result.d -= 1.0;
    assert( result.d < 1.0 && result.d >= 0);
    return( result.d );
}

#endif
#endif